The present invention relates to an apparatus for treating substrates, and includes at least one process container that is disposed in a gas atmosphere, contains a treatment fluid, and has at least two continuously open openings that are disposed below a treatment fluid surface and are provided for the linear guidance of the substrates through the container.
Such an apparatus, which is known, for example, from EP-A-0 817 246, is a static system with which the treatment fluid stands in the process container without moving. The result of this is that a process taking place in the container is adversely affected by contamination of the treatment fluid, especially in the region of the linear guidance of the substrates through the container. Thus, it is not possible to have a good and homogeneous treatment of the substrates.
Furthermore known from JP-A-5-291 223 is an apparatus for the treatment of substrates according to which a process container that can be filled with treatment fluid from above is provided with two lateral openings. The openings can be respectively closed off by closure elements in order during the treatment to prevent an escape of treatment fluid. Provided on the base of the process container is an outlet for the treatment fluid.
Proceeding from the above mentioned state of the art it is therefore an object of the present invention to provide an apparatus of the aforementioned general type that in a simple and economical manner enables a more homogeneous and improved treatment of substrates.
Pursuant to the present invention, the object is realized, for an apparatus for treating substrates having at least one process container that is disposed in a gas atmosphere, contains a treatment fluid and has at least two openings disposed below a treatment fluid surface for the linear guidance of the substrates therethrough, by an overflow means for the treatment fluid. The overflow means for the treatment fluid enables a continuous conveyance of treatment fluid through the process container. This prevents increased concentrations of contamination in certain regions of the process container, especially in the region of the linear guidance of the substrates, or changes in concentration of the cleaning media (consumption during the cleaning) are again compensated for. This ensures an improved and more homogeneous treatment of the substrates. Furthermore, by providing an overflow means, an essentially uniform treatment fluid level is ensured during the treatment in a simple and economical manner, and thus a more uniform pressure of the treatment fluid is ensured at the openings. Despite a flow of the treatment fluid, a uniform pressure can in a simple manner prevent the treatment fluid from flowing out of the process container.
Pursuant to one particularly preferred embodiment of the invention, the height of the overflow means can be adjusted in order to vary the treatment fluid level within the process container. This is particularly advantageous if within the process container treatments are carried out with different treatment fluids that have different densities, and, at the same fluid level, different pressure conditions would result at the openings that are disposed below the treatment fluid surface. These pressure conditions can be set via the height-adjustable overflow means in order to prevent the treatment fluid from flowing out of the openings.
A closed overflow container is preferably provided in order to enable a vacuum to be applied in an air space that is formed above the treatment fluid surface. By means of the vacuum an under pressure can be generated at the openings that are disposed below the treatment fluid surface in order to prevent the treatment fluid from flowing out. Especially in combination with the height-adjustable overflow edge, a simple control of the pressure conditions at the openings can be achieved. In the air space that is located above the treatment fluid a uniform vacuum is preferably provided. The pressure changes that result, for example, due to different treatment fluids (due to different densities) at the openings are preferably regulated by the height-adjustable overflow edge. To enable a good and uniform vacuum, the process container and the overflow container are closed off.
For a uniform and homogeneous flow within the process container, the treatment fluid can preferably be introduced into the process container via an essentially horizontally disposed diffuser plate. Pursuant to a further embodiment of the invention, a collecting trough is mounted on the outer periphery of the process container below at least one of the openings in order to prevent any treatment fluid that might escape from the process container from contaminating the area around the process container.
Pursuant to one preferred embodiment of the invention, at least one ultrasonic unit is provided within the process container in order by causing ultra-sound waves to act on the substrates to promote the treatment thereof, and in particular cleaning processes. In this connection the ultrasonic unit preferably extends over the entire width of the process container, and in particular perpendicular to the direction of movement of the substrates, and is also pivotable in order to provide a uniform impingement of ultra-sound waves over the entire surface of the substrates. To enable a uniform and homogeneous flow of the treatment fluid within the process container, the ultrasonic unit preferably has an aerodynamic shape, i.e. it has little resistance to flow in the direction of flow. For a good and uniform treatment of both surfaces of the substrate, it is preferably movable between at least two ultrasonic units.
Pursuant to a further embodiment of the invention, a drying chamber is provided that surrounds an outlet opening of the process container and that has a device for the introduction of a fluid that reduces the surface tension of the treatment fluid. By providing the drying chamber at the outlet opening, the previously treated substrates can be dried via the Marangoni effect immediately upon removal from the process container. The chamber preferably forms an essentially closed system, as a result of which a uniform N2/IPA atmosphere is ensured at the wafer exit.
Pursuant to a further, preferred embodiment of the invention, a plurality of process containers are disposed one after another. These containers make it possible for the substrates, without a necessary alteration of their orientation, to pass through a plurality of possibly different process steps. In this connection, the process containers preferably contain different treatment fluids in order to provide different process steps. A wetting unit is preferably provided between the process containers to prevent the substrates from drying out between the successive process steps, which could adversely affect successive process steps. The wetting unit is preferably designed in such a way that the substrates are initially rinsed, thereby preventing treatment fluid from passing from one process container to the next.